Inflammation: What It Is and How to Reduce It

What is inflammation?

Inflammation is your body’s natural way of fighting off infections, injuries and irritants. It causes redness, swelling, heat and pain.¹ When you sprain an ankle or get a sore throat, that is inflammation doing its job. Blood flow increases, immune cells arrive, and repair begins.

Acute and chronic inflammation

• Acute inflammation switches on fast, lasts days, and switches off when the job is done. These short bursts are critical for surviving injury and infection²
• Chronic inflammation is a low-level immune response that stays on for months or years. Researchers call it systemic chronic inflammation. It doesn’t cause the obvious redness and swelling of an injury, and you usually can’t feel it²

Chronic inflammation is thought to contribute to many of the leading causes of ill health, including heart disease, type 2 diabetes, chronic kidney disease, fatty liver disease, some cancers, and autoimmune and neurodegenerative conditions.²

This is different from inflammatory diseases such as rheumatoid arthritis, lupus and inflammatory bowel disease, where the immune system attacks a specific part of the body and causes clear symptoms.¹ Those need medical treatment. See types of arthritis.

What causes chronic inflammation?

The main drivers that researchers have identified are:²

• Physical inactivity
• Excess body fat, especially around the middle. Fat tissue is an active organ that releases inflammatory signals, and obesity is described as a state of low-grade inflammation throughout the body³
• A poor diet
• Long-term psychological stress
• Disturbed sleep
• Smoking, and exposure to pollutants
• Long-running infections

Can you test for inflammation?

The most common test is C-reactive protein, or CRP. CRP is made by the liver and rises quickly, within 24 to 48 hours, when there is inflammation, infection or tissue damage.¹

• A normal CRP is less than 5 mg/L
• A CRP above 10 mg/L means there is inflammation somewhere in the body
• The test can’t tell you where the inflammation is or what is causing it¹

A more sensitive version, called high-sensitivity CRP, is sometimes used alongside other risk factors to help assess the risk of heart disease.¹ CRP is also affected by age, sex and smoking, so results need to be read by your doctor in context.¹

Be wary of online lists of “signs of inflammation” such as tiredness, bloating or brain fog. These symptoms are real and worth sorting out, but they have many possible causes and are not a reliable sign of inflammation.

How to reduce inflammation in the body

Exercise regularly

A meta-analysis of 83 trials found that exercise training lowered CRP. The drop was bigger when people also lost body fat, but it happened without weight loss too, and at any age.⁴

Lose excess weight

A systematic review found that CRP fell by about 0.13 mg/L for every kilogram lost, in a roughly straight line.⁵ The biggest improvements in inflammatory markers are seen with a loss of at least 10 per cent of body weight.³

Eat a Mediterranean-style diet

That means mostly vegetables, fruit, legumes, wholegrains, nuts, fish and olive oil, with little processed food. A meta-analysis of 17 randomised trials with 2,300 people found that this pattern of eating lowered CRP by about 1 mg/L and lowered another marker, interleukin-6.⁶

The benefit comes from the overall pattern. No single “anti-inflammatory” food has been shown to do the same.

Eat fish, or consider fish oil

A meta-analysis of 68 randomised trials found that supplements of the omega-3 fats found in fish lowered CRP and other inflammatory markers, and the authors recommended taking them long term for the best effect.⁷ Eating oily fish a couple of times a week is the food-first way to get them.

Protect your sleep

An analysis of 72 studies with more than 50,000 people found that disturbed sleep was linked with higher CRP and interleukin-6. So was sleeping for a very long time.⁸ See sleep hygiene.

Manage stress

Laboratory studies show that inflammatory markers in the blood rise within an hour or two of a stressful task.⁹ Repeated often enough, that may be one route from long-term stress to poor health. See stress.

Don’t smoke

In a study that followed more than 1,600 smokers, heavier smoking went with higher white cell counts and other markers of inflammation. Those who quit improved within a year, whether or not they gained weight.¹⁰

What about supplements?

Many supplements are sold for inflammation. Apart from omega-3 fats, the evidence for most is thin, and none replaces the habits above. Check with your doctor or pharmacist before starting one, especially if you take other medicines.

Inflammation and pain

Inflammation is one source of pain, but long-term pain often continues without it. In many chronic pain conditions the nervous system itself has become more sensitive. See what is chronic pain? and central sensitisation.

When to see a doctor

• A joint that is swollen, warm and stiff, especially first thing in the morning
• Unexplained fevers, night sweats or weight loss
• Ongoing tiredness with aches and pains
• Persistent diarrhoea, or blood in your stool
• A wound or area of skin that is red, hot, swollen and getting worse

References

1. healthdirect. C-reactive protein (CRP) blood test.
2. Furman D, Campisi J, Verdin E, et al. Chronic inflammation in the etiology of disease across the life span. Nat Med. 2019;25(12):1822-1832.
3. Forsythe LK, Wallace JM, Livingstone MB. Obesity and inflammation: the effects of weight loss. Nutr Res Rev. 2008;21(2):117-33.
4. Fedewa MV, Hathaway ED, Ward-Ritacco CL. Effect of exercise training on C reactive protein: a systematic review and meta-analysis of randomised and non-randomised controlled trials. Br J Sports Med. 2017;51(8):670-676.
5. Selvin E, Paynter NP, Erlinger TP. The effect of weight loss on C-reactive protein: a systematic review. Arch Intern Med. 2007;167(1):31-9.
6. Schwingshackl L, Hoffmann G. Mediterranean dietary pattern, inflammation and endothelial function: a systematic review and meta-analysis of intervention trials. Nutr Metab Cardiovasc Dis. 2014;24(9):929-39.
7. Li K, Huang T, Zheng J, et al. Effect of marine-derived n-3 polyunsaturated fatty acids on C-reactive protein, interleukin 6 and tumor necrosis factor α: a meta-analysis. PLoS One. 2014;9(2):e88103.
8. Irwin MR, Olmstead R, Carroll JE. Sleep Disturbance, Sleep Duration, and Inflammation: A Systematic Review and Meta-Analysis of Cohort Studies and Experimental Sleep Deprivation. Biol Psychiatry. 2016;80(1):40-52.
9. Marsland AL, Walsh C, Lockwood K, et al. The effects of acute psychological stress on circulating and stimulated inflammatory markers: A systematic review and meta-analysis. Brain Behav Immun. 2017;64:208-219.
10. King CC, Piper ME, Gepner AD, et al. Longitudinal Impact of Smoking and Smoking Cessation on Inflammatory Markers of Cardiovascular Disease Risk. Arterioscler Thromb Vasc Biol. 2017;37(2):374-379.